LOANS - Consumer Troubled Debt Restructurings (Details) - Consumer $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($) loan	Jun. 30, 2021 USD ($) loan	Jun. 30, 2022 USD ($) loan	Jun. 30, 2021 USD ($) loan
Loans receivable
Period within which default occurred post-modification			1 year
Number of days past due, non-accrual status			60 days
In North America offices
Loans receivable
Number of loans modified | loan	37,307	36,949	78,643	96,851
Post-modification recorded investment	$ 221.0	$ 248.0	$ 485.0	$ 621.0
TDR loans in payment default	$ 74.0	$ 92.0	$ 135.0	$ 178.0
In North America offices | Residential mortgages
Loans receivable
Number of loans modified | loan	279	334	625	670
Post-modification recorded investment	$ 56.0	$ 60.0	$ 137.0	$ 120.0
Average interest rate reduction	0.00%	0.00%	0.00%	0.00%
Post-modification recorded investment for borrowers that have gone through Chapter 7 bankruptcy	$ 0.4	$ 4.0	$ 2.0	$ 7.0
TDR loans in payment default	13.0	15.0	17.0	33.0
In North America offices | Residential mortgages | New OCC guidance
Loans receivable
Post-modification recorded investment for borrowers that have gone through Chapter 7 bankruptcy	$ 0.4	$ 1.0	$ 2.0	$ 2.0
In North America offices | Home equity loans
Loans receivable
Number of loans modified | loan	103	53	207	112
Post-modification recorded investment	$ 7.0	$ 4.0	$ 16.0	$ 10.0
Average interest rate reduction	0.00%	0.00%	0.00%	0.00%
TDR loans in payment default	$ 2.0	$ 3.0	$ 2.0	$ 7.0
In North America offices | Credit cards
Loans receivable
Number of loans modified | loan	36,820	36,337	77,560	95,383
Post-modification recorded investment	$ 157.0	$ 181.0	$ 330.0	$ 481.0
Average interest rate reduction	18.00%	17.00%	17.00%	17.00%
TDR loans in payment default	$ 59.0	$ 73.0	$ 116.0	$ 136.0
In North America offices | Personal, small business and other
Loans receivable
Number of loans modified | loan	105	225	251	686
Post-modification recorded investment	$ 1.0	$ 3.0	$ 2.0	$ 10.0
Average interest rate reduction	5.00%	3.00%	5.00%	3.00%
TDR loans in payment default	$ 0.0	$ 1.0	$ 0.0	$ 2.0
In offices outside North America
Loans receivable
Number of loans modified | loan	4,167	25,607	10,022	58,211
Post-modification recorded investment	$ 24.0	$ 179.0	$ 61.0	$ 363.0
TDR loans in payment default	$ 7.0	$ 91.0	$ 16.0	$ 177.0
In offices outside North America | Residential mortgages
Loans receivable
Number of loans modified | loan	110	530	293	997
Post-modification recorded investment	$ 4.0	$ 28.0	$ 10.0	$ 52.0
Average interest rate reduction	0.00%	1.00%	0.00%	1.00%
TDR loans in payment default	$ 3.0	$ 10.0	$ 7.0	$ 22.0
In offices outside North America | Credit cards
Loans receivable
Number of loans modified | loan	3,462	18,297	8,462	42,896
Post-modification recorded investment	$ 13.0	$ 94.0	$ 35.0	$ 196.0
Average interest rate reduction	27.00%	12.00%	23.00%	14.00%
TDR loans in payment default	$ 3.0	$ 45.0	$ 7.0	$ 97.0
In offices outside North America | Personal, small business and other
Loans receivable
Number of loans modified | loan	595	6,780	1,267	14,318
Post-modification recorded investment	$ 7.0	$ 57.0	$ 16.0	$ 115.0
Average interest rate reduction	8.00%	10.00%	8.00%	10.00%
TDR loans in payment default	$ 1.0	$ 36.0	$ 2.0	$ 58.0
Deferred principal | In North America offices
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Deferred principal | In North America offices | Residential mortgages
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Deferred principal | In North America offices | Home equity loans
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0
Deferred principal | In North America offices | Credit cards
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Deferred principal | In North America offices | Personal, small business and other
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Deferred principal | In offices outside North America
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Deferred principal | In offices outside North America | Residential mortgages
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Deferred principal | In offices outside North America | Credit cards
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Deferred principal | In offices outside North America | Personal, small business and other
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Contingent principal forgiveness | In North America offices
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Contingent principal forgiveness | In North America offices | Residential mortgages
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Contingent principal forgiveness | In North America offices | Home equity loans
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Contingent principal forgiveness | In North America offices | Credit cards
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Contingent principal forgiveness | In North America offices | Personal, small business and other
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Contingent principal forgiveness | In offices outside North America
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Contingent principal forgiveness | In offices outside North America | Residential mortgages
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Contingent principal forgiveness | In offices outside North America | Credit cards
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Contingent principal forgiveness | In offices outside North America | Personal, small business and other
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Principal forgiveness | In North America offices
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Principal forgiveness | In North America offices | Residential mortgages
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Principal forgiveness | In North America offices | Home equity loans
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Principal forgiveness | In North America offices | Credit cards
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Principal forgiveness | In North America offices | Personal, small business and other
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Principal forgiveness | In offices outside North America
Loans receivable
Post-modification recorded investment	0.0	3.0	1.0	12.0
Principal forgiveness | In offices outside North America | Residential mortgages
Loans receivable
Post-modification recorded investment	0.0	0.0	0.0	0.0
Principal forgiveness | In offices outside North America | Credit cards
Loans receivable
Post-modification recorded investment		1.0	1.0	8.0
Principal forgiveness | In offices outside North America | Personal, small business and other
Loans receivable
Post-modification recorded investment	$ 0.0	$ 2.0		$ 4.0